Tapered implantable device and methods for making such devices

ABSTRACT

A tapered implantable device includes an ePTFE tubular member having a tapered length portion. The tapered length portion provides rapid recovery properties. The tapered length portion can feature a microstructure that includes a multiplicity of bent fibrils.

TECHNICAL FIELD

This document relates to tapered implantable devices and methods formaking such devices that may be used for providing a lumen for fluidflow in bodily cavities, organs, and vessels within a patient.

BACKGROUND

Medical devices are frequently used to treat the anatomy of patients.Such devices can be permanently or semi-permanently implanted in theanatomy to provide treatment to the patient. Frequently, these devices,including stents, grafts, stent-grafts, filters, valves, occluders,markers, mapping devices, therapeutic agent delivery devices,prostheses, pumps, bandages, and other endoluminal and implantabledevices, are inserted into the body at an insertion point and deliveredto a treatment site.

Devices such as grafts and stent-grafts are used in a variety of placesin the human body to repair, support, and/or replace anatomical lumens,such as blood vessels, respiratory ducts, gastrointestinal ducts, andthe like. Such devices can, for example, provide lumens for fluid flow.In such configurations, flexible and durable devices are needed.

In various applications, such as particular vascular applications, it isdesirable to utilize a graft or artificial lumen having a tapered lengthportion. Tapered length portion and/or grafts may also be useful inconnecting discreet grafts or tubes of differing diameters. As such,there is an ongoing need to provide tapered implantable devices, such asgrafts and/or stent-grafts, which have improved flexibility and/or rapidrecovery properties. Such devices may improve characteristics of theblood flow of a patient and reduce thrombosis.

SUMMARY

In a first general aspect, a tapered implantable device for repairing orreplacing a lumen in the body of a patient comprises a tubular member,such as an ePTFE tubular member, having a tapered portion. The taperedportion includes a multiplicity of substantially bent fibrils, providinga region having rapid recovery properties.

In various implementations, a tapered implantable device in accordancewith the present disclosure is formed by stretching a smaller diameterpolymeric tubular member over a first mandrel having larger and smalleropposing ends and an intermediate tapered length segment to create afirst tapered length portion on the polymeric tubular mandrel. Thetubular member is then longitudinally compressed on a second mandrel toform the tapered implantable device by converting the first taperedlength portion into a second tapered length portion having amultiplicity of bent fibrils. The tapered implantable device is thenremoved from the second mandrel and prepared for implantation into theanatomy of a patient.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and the drawings, andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a portion of a tapered implantable device inaccordance with the present disclosure;

FIG. 2 is a schematic representation of a microstructure of ePTFEmaterial in accordance with the present disclosure;

FIG. 3A is a side view of a first tapered mandrel, and FIG. 3B is a sideview of a tapered implantable device in a stage of formation; and

FIG. 4A is a side view of a second tapered mandrel, FIG. 4B is a sideview of a tapered implantable device in another stage of formation, andFIG. 4C is a side view of a second tapered mandrel and complimentaryfemale die.

Like reference symbols in the various drawings indicate like elements.It should also be noted that the accompanying drawing figures referredto herein are not all drawn to scale, but may be exaggerated toillustrate various aspects of the present disclosure, and in thatregard, the drawing figures should not be construed as limiting.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

This document describes devices, systems, and methods that are useful,for example, for repairing, supporting, and/or replacing anatomicallumens. Several implantable medical devices are described herein, and ingeneral any of the features described with respect to a particulardevice may also be used with any of the other devices described herein.In some examples, one or more features described with respect to aparticular device may be added to or included with another device. Also,various combinations or sub-combinations of any of the featuresdescribed herein may generally be used with any of the devices describedherein.

In general, any of the implantable devices described herein can bedelivered to, and deployed at, an in vivo deployment site within a bodyof a patient using various minimally invasive surgical techniques.Likewise, these devices may also be surgically implanted via vascularsurgical techniques.

Further, any of the implantable medical devices described herein can bedelivered to, and deployed at, an in vivo deployment site within a bodyof a patient using various minimally invasive transcatheter deploymenttechniques.

Any of the implantable medical devices discussed herein can be used torepair, replace, and/or provide support to a body lumen. In variousembodiments, implantable medical devices of the present disclosure canbe used in a body lumen, including those within the circulatory andgastrointestinal systems.

As used herein, “implantable” means implanted in the body of a patientfor more than 29 days.

As used herein, “taper” or “tapered” generally refers to a region oftransition from one portion of a device to another portion of the samedevice. Most typically, a taper transitions a portion of a tubulardevice having a circular transverse cross-section with a larger insidediameter to another portion of the same device having a circulartransverse cross-section with a smaller inner diameter. The region canbe symmetrically or asymmetrically conical, or may be shaped to includebumps, reversals, or flares.

For the sake of consistency and clarity, the term “portion” is used toidentify a length of, for example, a tubular member. The term “segment”is used to identify a length of, for example, a first or second mandrel.These terms are not intended to be limiting, and are chosen primarily toassist in understanding the references to various tubular members andmandrels.

FIG. 1 illustrates an example tapered implantable device 100 comprisinga polymeric tubular member 102 having a first smaller diameter lengthportion 104, a second larger diameter length portion 106, and a taperedlength portion 108. Polymeric tubular member 102 can, for example,comprise an axially compressible polymeric material, such as alongitudinally extruded and expanded polymer, including expandedpolytetrafluoroethylene (“ePTFE”), expanded modified PTFE, expandedcopolymers of PTFE, nylons, polycarbonates, polyethylenes,polypropylenes, polyurethanes and the like. In various embodiments,polymeric tubular member 102 comprises an extruded ePTFE tube, such asthe tubes described in U.S. Pat. Nos. 3,953,566 and 4,187,390. In otherembodiments, polymeric tubular member 102 comprises a wrapped ePTFE filmtube. For example, member 102 can comprise a tube made from an ePTFEfilm that has been cigarette wrapped on the surface of a mandrel or,alternatively, has been helically wrapped on the surface of a mandrel.Such ePTFE films of this type can be made generally as taught by U.S.Pat. Nos. 3,953,566 and 4,187,390. In yet other embodiments, member 102can comprise a polymeric open celled material. However, any suitablepolymeric tubular member is within the scope of the present disclosure.

In various embodiments, polymeric tubular member 102 comprises an ePTFEtube having microstructure of nodes interconnected by fibrils. Themicrostructure of polymeric tubular member 102 can comprise amultiplicity of fibrils having a mean fibril length. Mean fibril lengthcan be determined, for example, by examining a photomicrograph of thesurface of polymeric tubular member 102 and by taking the mean of tenmeasurements made in the predominant direction of the fibrils betweennodes connected by fibrils. First, a photomicrograph is made of arepresentative region of the sample surface, of adequate magnificationto show at least five sequential fibrils within the length of thephotomicrograph. A series of five measurements are taken along astraight line drawn onto the surface of the photomicrograph in thepredominant direction of the fibrils followed by a second series of fivemeasurements made along a second line drawn parallel to the first. Ameasurement constitutes the distance between adjacent nodes connected byat least one fibril. The ten measurements obtained by this method areaveraged to obtain the mean fibril length of the region.

For example, as illustrated in FIG. 2, any or all of length portions102, 108, and 106 can have a multiplicity of bent fibrils 214.

Tapered length portion 108 can, for example, possess a rapid recoveryproperty, i.e., a spring-like property. Rapid recovery as herein definedis the difference between the extended length of a material and therecovered length with respect to the recovered length, as generallydescribed in U.S. Pat. No. 5,026,513. The extended length is the lengthof material under tensile load and recovered length is the length ofmaterial. In various embodiments, rapid recovery can be quantified bythe following equation:RR %=(I _(t) −I _(r))×100% (I _(r))where I_(t) is the length of the tapered length portion 108 whenextended axially under 1% maximum tensile force, and I_(r) is the lengthof the tapered portion five seconds after the release of the tensileforce. Tapered length portion 108 having rapid recovery properties can,for example, exhibit improved bending characteristics and improvedresistance to kinking, constriction, and/or collapse under bending.

In various embodiments, tapered length portion 108 can comprise auniform frustoconical section. In such embodiments, tapered lengthportion 108 expands in the manner of a uniform frustoconical sectionfrom a diameter of first smaller diameter length portion 104 to adiameter of second larger diameter length portion 106.

In other embodiments, tapered length portion 108 comprises a non-uniformshape. For example, tapered length portion 108 can expand from adiameter of first smaller diameter length portion 104 to a diameter ofsecond larger diameter length portion 106 in a non-uniform manner, suchas a curved, non-linear shape. Any shape of tapered length portion 108is within the scope of the present disclosure.

A method for making a tapered implantable device of the presentdisclosure is described as follows. A polymeric tubular member is fittedover a first mandrel having first, longer tapered length segment to forma first tapered length portion along a portion of the length of thepolymeric tubular member. The polymeric tubular member is removed fromthe first mandrel and fitted over and axially compressed onto a secondmandrel having a second, shorter tapered length segment to form thefirst tapered length portion into a second tapered length portion. Afemale die can optionally be used assist in compression of the polymerictubular member on the second mandrel, particularly over the secondtapered length portion. The polymeric tubular member can then be removedfrom the second mandrel.

FIGS. 3A and 3B illustrate an example step in a method to form a taperedimplantable implant. Polymeric tubular member 102 is fitted over a firstmandrel 330. First mandrel 330, as shown in FIG. 3A, comprises a smallerdiameter length segment 334, a larger diameter length segment 336, and afirst, longer tapered length segment 338. First, longer tapered lengthsegment 338 is typically located between smaller diameter length segment334 and larger diameter length segment 336.

In various embodiments, polymeric tubular element 102 initiallycomprises a diameter (consistent along its length) equal to or slightlyless than the diameter of smaller diameter length segment 334. Polymerictubular member 102 is placed around the exterior surface of firstmandrel 330 and pulled onto the mandrel in the direction of the firstlarger diameter length segment 336. In various embodiments, as polymerictubular member 102 is fitted over first mandrel 330 it is stretched overfirst, longer tapered length segment 338 to larger diameter lengthsegment 336, forming second larger diameter length portion 106 andtapered portion having a first longer length 318.

In various embodiments, the respective lengths of larger diameter lengthportion 104 and smaller diameter length portion 106 can be selected toposition tapered portion having a first longer length 318 at a desiredposition onto polymeric tubular member 102. For example, a taperedimplantable device having a particular length of a larger diameter andparticular length of a shorter diameter may be desired. It can also beappreciated that the tapered implantable device may be continuouslytapered between the opposing ends of the device. By providing a methodfor placing a tapered portion having a multiplicity of bent fibrilsbetween a smaller diameter length portion 104 and a larger diameterlength portion 106, a tapered implantable device 100 having at leastsufficient length of smaller diameter length portion 104 and largerdiameter length portion 106 can be formed. In such embodiments, taperedimplantable device 100 can be sized by, for example, cutting one or bothends of polymeric tubular member 102 such that a sufficient length ofsmaller diameter length portion 104 and larger diameter length portion106 is provided.

Prior to removal of polymeric tubular member 102 from first mandrel 330,member 102 can be exposed to further processing steps. For example,polymeric tubular member 102 can be wrapped with a biocompatiblereinforcing film, such as an ePTFE film. Any biocompatible materialcapable of reinforcing polymeric tubular member 102 is within the scopeof the present disclosure.

For example, a length portion of polymeric tubular member 102, such astapered length portion with a first longer length 318, can be heated.Further, heat can be applied to the entire first mandrel 330 andpolymeric tubular member 102. Any processing of polymeric tubular member102, including tapered length portion having a first longer length 318,is within the scope of the present disclosure.

In various embodiments, the outer surface of porous tubular member 102can be coated with an elastomer. For example, as referenced in U.S. Pat.No. 8,029,563, a silicone composition such as MED-1137 Adhesive SiliconeType A from NuSil Silicone Technology (Carpenteria, Calif.) can beapplied to the outer surface of porous tubular member 102. In variousembodiments, the elastomer is applied after porous tubular member 102 isheated. Any application of elastomer to porous tubular member 102 iswithin the scope of the present disclosure.

Further, prior to removal from first mandrel 330, porous tubular member102 can be surrounded by an optional second porous tubular member. Invarious embodiments, the optional second porous tubular member comprisesa larger inner diameter than an outer diameter of the porous tubularmember 102. The optional second porous tubular member can be positionedconcentrically around first tubular member 102 on mandrel 330.

As illustrated in FIG. 4A, a second mandrel 440 can comprise a largerdiameter length segment 446, a smaller diameter length segment 444, anda second, shorter tapered length segment 448. Second, shorter taperedlength segment 448 is typically located between smaller diameter lengthsegment 444 and larger diameter length segment 446.

With reference to FIG. 4B, polymeric tubular member 102 having a taperedportion with a first longer length 318 can be fitted over second tubularmandrel 440 such that tapered length portion 318 is located at or nearsecond, shorter tapered length segment 448. Polymeric tubular member 102can then be compressed longitudinally along second mandrel 440 in thedirection of a larger diameter length segment 446, which convertstapered portion having a first longer length 318 to a tapered portionhaving a second shorter length 108. In such embodiments, shorterdiameter length portion 104 and longer diameter length portion 106 ofpolymeric tubular member 102 do not experience a significant lengthchange, as only tapered portion having a first longer length 318 iscompressed against an exterior surface of second mandrel 440. As such,as previously described, the desired dimensions of tapered implantabledevice 100 can be selected prior to formation of tapered portion havinga second shorter length 108.

A compression ratio can be used to describe the amount of longitudinalcompression applied to tapered portion having a first longer length 318.For example, a compression ratio can comprise a ratio of the lengthtapered portion having a second shorter length 108 to the length oftapered portion having a first longer length 318. In variousembodiments, the compression ratio can be between about 75% and 95%. Inother embodiments, the compression ratio can be between about 50% and75%. In yet other embodiments, the compression ratio can be betweenabout 25% and 50%. The compression ratio may range as low as about 15%,and is largely dependent on the bulk density of the chosen porousprecursor material.

In various embodiments, the compression ratio can correlate with therespective lengths of tapered portion having a second shorter length 108and tapered portion having a first longer length 318. For example, amandrel ratio can comprise the ratio of the length of second, shortertapered length segment 448 to the length of first, longer tapered lengthsegment 338. Preferably, the compression ratio and the mandrel ratio aresubstantially the same. In other embodiments, the mandrel ratio iswithin 10% of the compression ratio. In yet other embodiments, themandrel ratio is within 33% of the compression ratio. Any correlationbetween the compression ratio and the mandrel ratio is within the scopeof the present disclosure.

In various embodiments, as illustrated in FIG. 4C, a female die 450 canbe used to assist in formation of tapered portion having a secondshorter length 108. For example, female die 450 can apply alongitudinally compressive force against polymeric tubular member 102 ator near second, shorter tapered length segment 448, causing taperedportion having a first longer length 318 to compress against second,shorter tapered length segment 448 of second mandrel 440. Female die 450can comprise, for example, a complementary shape to second, shortertapered length segment 448 of second mandrel 440. In other embodiments,female die 450 comprises a shape different from that of second, shortertapered length segment 448. In such embodiments, female die 450 canassist in providing a desired shape on an external surface of polymerictubular member 102, including tapered portion having a second shorterlength 108.

Further, female die 450 can assist in providing a consistent thicknessof polymeric tubular member 102 in the smaller diameter region 104and/or the tapered portion having a second shorter length 108. Anyconfiguration of female die 450 that assists in forming tapered portionhaving a second shorter length 108 in a porous tubular member is withinthe scope of the present disclosure.

Prior to removal of polymeric tubular member 102 from second mandrel440, member 102 can be exposed to further processing steps. For example,a portion of polymeric tubular member 102, such as tapered portion witha second shorter length 108, can be heated. Further, heat can be appliedto the entire second mandrel 440 and polymeric tubular member 102. Anyprocessing of polymeric tubular member 102, including tapered portionhaving a second shorter length 108, is within the scope of the presentdisclosure.

After formation of tapered portion having a second shorter length 108,tapered implantable device 100 can be removed from second mandrel 440and prepared for use in the anatomy of a patient. In variousembodiments, tapered implantable device 100 can be combined with amedical device such as, for example, a stent. In other embodiments,tapered implantable device 100 can be used without combination withanother medical device. In such embodiments, tapered implantable device100 can comprise a graft. Although described in particular embodiments,tapered implantable device 100 can be used alone or in combination withany suitable medical device for implantation within the anatomy of apatient.

Several characteristics and advantages have been set forth in thepreceding description, including various alternatives together withdetails of the structure and function of the devices and methods. Thedisclosure is intended as illustrative only and as such is not intendedto be exhaustive or limiting. It will be evident to those skilled in theart that various modifications may be made, especially in matters ofstructure, materials, elements, components, shapes, sizes, andarrangements of parts including combinations within the principlesdescribed herein, to the full extent indicated by the broad, generalmeaning of the terms in which the appended claims are expressed. To theextent that these various modifications depart from the spirit and scopeof the appended claims, they are intended to be encompassed therein.

What is claimed is:
 1. A method of forming a tapered implantable articlewith a longitudinally compressed tapered portion, the method comprising:forming a tapered portion having a first longer length in an ePTFEtubular member using a first mandrel having a first, longer taperedlength segment; removing the ePTFE tubular member from the firstmandrel; longitudinally compressing the tapered portion having a firstlonger length of the ePTFE tubular member on a second mandrel having asecond, shorter tapered length segment into a tapered portion having asecond shorter length, wherein the second shorter length is at least 15%shorter than the first longer length; and removing the ePTFE tubularmember from the second mandrel, the longitudinally compressed taperedportion maintaining the second shorter length following removal from thesecond mandel.
 2. The method of claim 1, wherein a compression ratiocomprises the ratio of the tapered portion having a first longer lengthto the tapered portion having a second shorter length and a mandrelratio comprises a ratio of a length of the first, longer tapered lengthsegment to a length of the second, shorter tapered length segment,wherein the mandrel ratio is within 33% of the compression ratio.
 3. Themethod of claim 2, wherein the mandrel ratio is within 10% of thecompression ratio.
 4. The method of claim 2, wherein the compressionratio and the mandrel ratios are substantially the same.
 5. The methodof claim 1, wherein the step of forming a tapered portion having a firstlonger length in an ePTFE tubular member comprises pulling an extrudedePTFE tube over the first mandrel.
 6. The method of claim 1, wherein theePTFE tubular member comprises a multiplicity of fibrils, wherein amajority of the fibrils are bent.
 7. The method of claim 1, wherein thetapered portion having a first longer length and the tapered portionhaving a second shorter length comprise transverse cross sectionalshapes of equal diameter.
 8. The method of claim 1, wherein the taperedportion having a second shorter length comprises a uniform,frustoconical shape.
 9. The method of claim 1, wherein the taperedportion having a second shorter length having a non-linear taper. 10.The method of claim 1, further comprising the step of heating the ePTFEtubular member after longitudinally compressing the tapered portion ofthe ePTFE tubular member on the second mandrel.
 11. The method of claim1, wherein the step of longitudinally compressing the tapered portionhaving a first longer length on a second mandrel further comprisescompressing the ePTFE tubular member with a female die having acomplimentary shape to a shape of the second, shorter tapered lengthsegment.
 12. The method of claim 1, further comprising the step ofwrapping a film around at least a portion of an abluminal surface of theePTFE tubular member when the ePTFE tubular member is in the firstlonger length.
 13. The method of claim 1, wherein the ePTFE tubularmember has a first smaller diameter portion having a constant diameter,a second larger diameter portion having a constant diameter that islarger than the constant diameter of the smaller diameter portion, andfurther wherein the tapered portion is located between the first smallerdiameter portion and the second larger diameter portion.